Metal ion secondary batteries having solid electrolyte layers formed from flame-retardant solid electrolytes (e.g. lithium ion secondary battery, hereinafter it may be referred to as “all-solid-state battery”) have advantages such as they can easily simplify the system for securing safety.
As a technique related to such an all-solid-state battery, for example Patent Literature 1 discloses a technique of forming a LiNbO3 coating layer on the surface of a LiCoO2 powder, through a process of hydrolyzing an alkoxide solution including lithium and niobium on the surface of the LiCoO2 powder particle. Patent Literature 2 discloses a lithium-transition metal oxide powder consisting of a lithium-transition metal oxide particle at least apart of whose surface is covered by a coating layer including lithium niobate, whose carbon content is no more than 0.03 mass %. Non-Patent Literature 1 discloses a technique relating to a low temperature synthesis of lithium niobate with a peroxide route.